Concerted Carrier-Barrier Dynamics in van der Waals Schottky Junctions Revealed by Time-Resolved Atomic Force Microscopy

TL;DR

This study employs time-resolved atomic force microscopy to directly observe and analyze the ultrafast carrier and barrier dynamics at van der Waals Schottky junctions, revealing key processes that influence device performance.

Contribution

It introduces a novel real-space measurement technique to visualize nanoscale carrier-barrier interactions in TMDC-based junctions, advancing understanding of ultrafast interfacial dynamics.

Findings

Nanoscale Schottky barrier modulation occurs on nanosecond timescales.

Carrier dynamics are driven by the interplay of photoexcited carriers and barrier response.

The method reveals processes critical for optimizing optoelectronic device performance.

Abstract

Schottky junctions based on transition-metal dichalcogenides (TMDCs) have emerged as key building blocks for next-generation optoelectronic devices that demand ultrafast response and high sensitivity. However, the ultrafast, nanoscale carrier dynamics at these interfaces, crucial for device performance, have remained experimentally elusive. Here, we introduce optical pump-probe time-resolved atomic force microscopy to directly visualize, in real space, the nanosecond-scale modulation of the Schottky barrier potential at a van der Waals junction formed by point contact between WSe2 and a PtIr tip. Complementary analyses using transient absorption spectroscopy and light-modulated current-voltage characteristics together with model simulations reveal that time-resolved currents originate from the concerted temporal evolution of photoexcited carriers and the subsequent barrier response, processes that also define the rate-limiting steps of the photocurrent. Our results uncover the essential interfacial dynamics that underpin TMDC-based photodetectors and photovoltaic elements, while establishing a new measurement paradigm that complements and extends existing spectroscopic techniques. This approach provides direct access to nonequilibrium processes hidden at nanoscale interfaces, offering a powerful route to rational design of high-performance optoelectronic devices.